This continuation application takes its impetus from the significant findings of the current study, which reported the existence of a characteristic profile of quantitative EEG (QEEG) changes associated with cocaine dependence, and demonstrated persistence of this profile during six months of abstinence. Further, subtypes were found with distinctive QEEG profiles at baseline (5-14 days abstinent). Significant interactions existed between QEEG subtype, gender, comorbidity, and treatment outcome; A regression equation using a subset of QEEG baseline measures yielded highly significant (p<O.OOOl) predictions of length of stay in treatment. Theoretically, these electrophysiological results may be consistent with a model of pathophysiology of cocaine dependence based on neural sensitization due to chronic cocaine exposure. Alternatively, they may suggest differential neurophysiological vulnerability predisposing individuals to cocaine addiction or drug-seeking behavior. To appropriately explore the important implications of the current findings requires expansion of the study population, and lengthening of follow-up testing to abstinence intervals up to 18 months. Continuity with the current study is essential to maximize the total longitudinal sample size. Evaluations will include the current electrophysiological, psychiatric, and neuropsychological components. Using attrition estimates based upon those actually encountered in the current study, N's will be large enough at each interval, and in each gender, for sufficient power to test the hypotheses proposed. This continuation study will extend existing knowledge into periods of abstinence longer than currently reported. In addition, the heterogeneity of this baseline QEEG profile (subtypes) will be further analyzed in this larger population, with focus on the predictive relationship between subtype membership and outcome (continued abstinence). Special attention will be given to better understanding of the relationship of these findings to the significant interactions with gender and comorbidity.